This invention relates to an unloading mechanism for a combine grain tank and particularly to a two-stage system consisting of a generally upright auger conveyor carrying grain upwards from the grain tank and a generally horizontal auger conveyor to carry grain to a discharge point alongside the combine.
A particular advantage of such two-stage systems compared with earlier conventional unloading systems, in which a single auger conveyor extends outwards and upwards from a discharge point at the bottom of a grain tank, is that they provide inherently more clearance for maneuvering trucks and wagons alongside the combine and beneath the discharge point. This advantage is enhanced if swivel means are provided for swingably adjusting the position of the unloading auger conveyor during the unloading operation for better distribution of the grain in truck or wagon. Other advantages are that, typically, these are closed conveyor systems so that no grain is lost upon the ground if the unloading auger conveyor is moved to transport position while grain remains in the system, and the drive need not be interrupted while the unloading conveyor is being repositioned.
Typically, in two-stage systems, the unloading auger conveyor is swung to a fore-and-aft position for transport, when it is desirable to have it generally horizontal so as to maintain a minimum overall transport height. In that case, however, it becomes desirable when unloading for the discharge point to be elevated somewhat with respect to the inner end of the unloading auger conveyor to gain additional overhead clearance for the receiving vehicle. In existing applications of the two-stage unloading system concept, elevation of the unloading auger conveyor is achieved by making the axis of its swivel means coaxial with the axis of the upright auger conveyor but inclining the upright auger conveyor to the rear. The angle between the unloading and upright auger conveyor is typically greater than 90.degree. so that, when swung into the unloading zone, the unloading auger conveyor becomes elevated above the horizontal. The disadvantage of this approach is that the rearward inclination of the upright auger conveyor and hence the fore-and-aft location of the unloading zone are dependent on the angle of elevation above the horizontal chosen for the unloading auger conveyor when in the unloading zone.
For transport it is convenient to swing the unloading auger conveyor of a two-stage unloading system so that it lies fore and aft along the upper edge of the grain tank and it is undesirable that it extend beyond the rear of the combine. But when the upright auger conveyor is inclined to the rear, rearward longitudinal space available for securing the unloading auger conveyor in transport position is severely limited.
Rearward inclination of the upright auger conveyor may also place the unloading zone so far to the rear as to make it difficult for the operator to monitor the unloading operation, especially when unloading on the move.
These limitations are becoming increasingly significant as combine field capacities continue to increase, grain tanks get bigger and unloading auger conveyors heavier and longer.
As grain tanks become larger there is more tendency to use tank configurations with more depth, both so as to avoid increases in overall height of the combine and also to maintain a low center of gravity for stability. An example of such a configuration is the so-called saddle tank straddling the combine. In such cases the outlet from the grain tank is often lower and further to the rear than in previous designs, thus compounding the problems arising from a rearward inclination of the upright auger conveyor.
As unloading auger conveyors become longer there is an increasing need for means of adjusting their angle of inclination to the horizontal, for example, to obtain proper register with support means which may be provided on the combine to support the unloading auger conveyor in the transport position. When the angle between the axes of the unloading and upright auger conveyor is fixed as in existing designs, provision of such an adjustment is not practicable.